Sorry for the necropost, but I was looking at the Plasma issue because I am considering buying some Gorn ships.
How about increasing the granularity a little for damage a bit, but do it in a different way? Instead of losing dice due to range, keep the dice and apply a die roll modifier when rolling damage.
Average damage as things are now:
Proposed change with a die roll modifier to each torpedo (torpedo retains original dice, but each die is less effective):
So this gives the plasma-firer an incentive to get closer to fire than 8". It also reduces the effectiveness of Plasma-Rs at long range, but as usual you can still roll lots of 5-6's and score some damage. Plasma-S actually benefits.
***edit, whoops, forgot the result for some plasmas at range 16: Plas-G does 4.5, Plas-F does 3, Plas-D does 1.5. Rationale: the target may be closing on the firing ship, and the torp arrives before it runs out of endurance, which is why plas-f and D can hit something at range 16...not strictly in accord with SFB, but the whole direct fire plasma thing is a kludge anyways.
***
As for the perceived over-effectiveness of IDF vs plasma, how about this:
In SFB, firing at long range at small targets (shuttles, drones, can't remember about plasma) gave a +1 modifier (harder to hit) at over range 12 (I think it was). This is partially recreated in that there is a -1 to fire against shuttles. How about applying that to firing at any seeking weapon over 6" away (half of the 12" in SFB)?
The net effect would be to be still allow one to use long-range phaser fire, but it will be less effective (ie, a P-1 at over 9" now requires a 3-6 to hit, the change would reduce it to 4-6).
What do you all think about this?